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Giberson and Collins Make Outdated Argument That Feathers Evolved From Scales

Casey Luskin
Links to this 6-Part Series Reviewing The Language of Science and Faith:

Part 1: ‘Junk DNA’ and ‘Pseudogene’ Arguments Pushed Into Increasingly Small Gaps in Scientific Knowledge
Part 2 (This Article): Outdated Argument That Feathers Evolved From Scales
Part 3: Rebutting Arguments for Eye Evolution
Part 4: Does Neanderthal Argument Demonstrate “Common Ancestry”?
Part 5: Giberson and Collins Commit Berra’s Blunder While Arguing for Macroevolution
Part 6: Contradictions, Irony, and Appeals to Authority Permeate The Language of Science and Faith
• The full review can be found here.

In my previous article, I noted that Karl Giberson and Francis Collins have relied upon some dangerous and historically weak arguments for evolution in their new book The Language of Science and Faith. They claim that a pseudogene that is “broken DNA” has “established conclusively” that macroevolution is valid and humans share common ancestry with apes. But given the many functions being discovered for pseudogenes, they may find that their argument for “broken DNA” itself becomes overturned by future discoveries. In fact, another one of their other main arguments for evolution in their book – that feathers evolved from scales – has already been overturned.

In at least two places in The Language of Science and Faith, Giberson and Collins cite scales evolving into feathers as evidence of the power of mutations:

“Many less dramatic changes are displayed as well, including animals developing feathers from ancestors with scales…” (p. 35)

“Over time, mutations in DNA can produce novel features, as we noted earlier, like feathers evolving from scales…” (p. 38)

There’s a significant problem with their argument: Even Leading evolutionary scientists today have abandoned the hypothesis that feathers evolved from scales.

The classical model of feather origins did claim that feathers evolved when scales on reptiles mutated to become frayed. Somehow these frayed scales gave the reptile an advantage of increased lift, eventually leading to the evolution of flight feathers.

The problem with this hypothesis is that feathers and scales are very different structures. Feathers essentially develop as hollow tubes that grow out of special follicles in the skin, whereas scales are flat, folded skin that develop quite differently.

Critics also argue that feathers are so well-suited for flight that there would have to be many transitional stages between scales and fully functional flight feathers. A 2003 article in Scientific American by Richard O. Prum (now at Yale) and Alan H. Brush (University of Connecticut) stated that the lack of evidence for the “scale” hypothesis meant the “long-cherished view of how and why feathers evolved has now been overturned.” The article continues:

Progress in solving the particularly puzzling origin of feathers has also been hampered by what now appear to be false leads, such as the assumption that the primitive feather evolved by elongation and division of the reptilian scale … The new evidence from developmental biology is particularly damaging to the classical theory that feathers evolved from elongate scales. According to this scenario, scales became feathers by first elongating, then growing fringed edges, and finally producing hooked and grooved barbules. As we have seen, however, feathers are tubes; the two planar sides of the vane–in other words, the front and the back–are created by the inside and outside of the tube only after the feather unfolds from its cylindrical sheath. In contrast, the two planar sides of a scale develop from the top and bottom of the initial epidermal outgrowth that forms the scale.

(Richard O. Prum and Alan H. Brush, “Which came first, the feather or the bird?,” Scientific American (March, 2003):84-93.)

Likewise, Gill’s authoritative 2007 textbook Ornithology states:

We long presumed that feathers evolved from scales of some kind, centering the debate on what advantages promoted the evolution of feathers from scales. More likely, feathers evolved not as modified scales but as a novel epidermal structure.

(Frank B. Gill, Ornithology, p. 39 (3rd. Ed., W.H. Freeman 2007).

The evo-devo explanation for feather origins offered by Prum and Bush in place of the scale hypothesis is little better. According to the latest hypothesis, feathers and other advanced features which allow birds to fly did not originally evolve from scales or for the purpose of flight. As Gill puts it, “feathers did not evolve initially in concert with the evolution of flight.” (p. 39) Instead, Prum and Bush’s Scientific American article vaguely proposes that feathers provided “some kind of survival advantage,” perhaps providing insulation for the organism. Their evo-devo model entails significant jumps in morphology, with a rachis, barbs, and barbules appearing abruptly, for no apparent reasons. Since there is no flight until all of those structures are in place, it’s difficult to understand what survival advantage these could have conferred.

Failing to explain the evolution of flight, evolutionists now expect us to believe that feathers and other complex features which are finely-tuned for flight are accidental byproducts that evolved for entirely different purposes. In other words, birds just got very, very lucky.

Additionally, proponents of the gradual evolution of feathers must explain a striking fact: the feathers of the earliest bird, Archaeopteryx, are essentially identical to those of today’s birds. Apparently little change has taken place over eons of time, even though great amounts of change were required.

While Giberson and Collins paint a rosy picture of the ability of mutations to produce novel features, Prum and Brush make a striking admission that evolutionary biology is struggling to explain how such novel features arise:

The origin of feathers is a specific instance of the much more general question of the origin of evolutionary novelties–structures that have no clear antecedents in ancestral animals and no clear related structures (homologues) in contemporary relatives. Although evolutionary theory provides a robust explanation for the appearance of minor variations in the size and shape of creatures and their component parts, it does not yet give as much guidance for understanding the emergence of entirely new structures, including digits, limbs, eyes and feathers.

(Richard O. Prum and Alan H. Brush, “Which came first, the feather or the bird?,” Scientific American (March, 2003):84-93.)

Rather than address or admit these fundamental problems with modern evolutionary biology, apparently Giberson and Collins have chosen to simply claim that feathers evolved from scales, a theory now disavowed by leading experts in the field.

Those Who Live in Glass Houses…
Ironically, The Language of Science and Faith complains that “[t]he evangelical literature is so filled with misrepresentations and outdated information about evolution.” (p. 34) If their accusation is true, then it would seem their book’s outdated arguments about feather evolution are not helping to solve that problem.


Casey Luskin

Associate Director, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.



Francis CollinsKarl Giberson